Dredges have been used for many years to remove submerged material from the bottom of lakes, harbors and other water areas. Reasons for engaging in dredging include deepening waterways to facilitate marine navigation, removal of bottom pollutants, recovery of bottom materials which have commercial value, and others.
Many common dredging devices are large, very expensive, and of limited use. For example, many hydraulic and pneumatic dredges will operate efficiently only in deep water, or only when excavating and removing a particular type of bottom material. Clam-shell dredges, crane buckets and other mechanical dredging devices operate efficiently only when excavating other types of bottom material, and can be expensive to operate. Most dredges require extensive ancillary systems to support the dredge, or to carry away the dredged material, or both.
In the past several years, a submergible pneumatic-hydraulic dredge pump has been offered to overcome some of these problems, but it has met with only limited success. Operators have discovered that this pump works only in relatively deep water, and with loose material which need not be aggressively cut or separated from surrounding bottom material. In some situations, pump operation has tended to cause pump movement; this pump movement can be expensive and difficult to control. If pump operations cannot be carefully monitored, the dredging operation can be so inefficient as to cause the pump operator serious financial difficulty.
It is accordingly the general object of this invention to provide a pneumatic-hydraulic pump dredge which can operate efficiently in deep or shallow water, and which can efficiently, precisely excavate a wide variety of materials.
Another object is to provide a pneumatic-hydraulic pump dredge and associated system which permits the pump to be located precisely at a given dredging spot, and permits the pump to be moved with relatively great precision over the area to be dredged. An associated object is to provide such a dredge which will not cause excessive turbidity and pollution in water adjacent the dredging site.
Yet another object is to offer an improved pneumatic-hydraulic pump which can be constructed and operated at relatively low cost, yet which is reliable in service and rugged in design.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings. Throughout the drawings, like reference numerals refer to like parts.